Hi! This patch attempts to fix some overflows during computation of the size and then effectively uses MIN (SSIZE_MAX, user_specified_value) as the bound.
Not really sure what exact behavior we want, whether that, or default to SSIZE_MAX (note the documentation mistakenly talks about SIZE_MAX / 2 instead) and use MIN (SIZE_MAX, user_specified_value) for user specified value, or error out if user_specified_value is larger than SSIZE_MAX or larger than SIZE_MAX. Also the else unit = 0; case probably should get diagnostics. Another issue is if we want to diagnose, that right now it will be diagnosed only if some allocation routine is seen, diagnosing stuff during option processing is unfortunately too early because we don't have sizetype/ssizetype built yet. Anyway, the following has been bootstrapped/regtested on x86_64-linux and i686-linux. 2017-08-03 Jakub Jelinek <ja...@redhat.com> PR driver/81650 * calls.c (alloc_max_size): Use HOST_WIDE_INT_UC (10??) instead of 10??LU, perform unit multiplication in wide_int, don't change alloc_object_size_limit if the limit is larger than SSIZE_MAX. * gcc.dg/pr81650.c: New test. --- gcc/calls.c.jj 2017-06-12 12:42:01.000000000 +0200 +++ gcc/calls.c 2017-08-02 13:41:00.887324420 +0200 @@ -1222,32 +1222,38 @@ alloc_max_size (void) else if (!strcasecmp (end, "KiB") || strcmp (end, "KB")) unit = 1024; else if (!strcmp (end, "MB")) - unit = 1000LU * 1000; + unit = HOST_WIDE_INT_UC (1000) * 1000; else if (!strcasecmp (end, "MiB")) - unit = 1024LU * 1024; + unit = HOST_WIDE_INT_UC (1024) * 1024; else if (!strcasecmp (end, "GB")) - unit = 1000LU * 1000 * 1000; + unit = HOST_WIDE_INT_UC (1000) * 1000 * 1000; else if (!strcasecmp (end, "GiB")) - unit = 1024LU * 1024 * 1024; + unit = HOST_WIDE_INT_UC (1024) * 1024 * 1024; else if (!strcasecmp (end, "TB")) - unit = 1000LU * 1000 * 1000 * 1000; + unit = HOST_WIDE_INT_UC (1000) * 1000 * 1000 * 1000; else if (!strcasecmp (end, "TiB")) - unit = 1024LU * 1024 * 1024 * 1024; + unit = HOST_WIDE_INT_UC (1024) * 1024 * 1024 * 1024; else if (!strcasecmp (end, "PB")) - unit = 1000LU * 1000 * 1000 * 1000 * 1000; + unit = HOST_WIDE_INT_UC (1000) * 1000 * 1000 * 1000 * 1000; else if (!strcasecmp (end, "PiB")) - unit = 1024LU * 1024 * 1024 * 1024 * 1024; + unit = HOST_WIDE_INT_UC (1024) * 1024 * 1024 * 1024 * 1024; else if (!strcasecmp (end, "EB")) - unit = 1000LU * 1000 * 1000 * 1000 * 1000 * 1000; + unit = HOST_WIDE_INT_UC (1000) * 1000 * 1000 * 1000 * 1000 + * 1000; else if (!strcasecmp (end, "EiB")) - unit = 1024LU * 1024 * 1024 * 1024 * 1024 * 1024; + unit = HOST_WIDE_INT_UC (1024) * 1024 * 1024 * 1024 * 1024 + * 1024; else unit = 0; } if (unit) - alloc_object_size_limit - = build_int_cst (ssizetype, limit * unit); + { + wide_int w = wi::uhwi (limit, HOST_BITS_PER_WIDE_INT + 64); + w *= unit; + if (wi::ltu_p (w, alloc_object_size_limit)) + alloc_object_size_limit = wide_int_to_tree (ssizetype, w); + } } } } --- gcc/testsuite/gcc.dg/pr81650.c.jj 2017-08-02 14:52:22.864787221 +0200 +++ gcc/testsuite/gcc.dg/pr81650.c 2017-08-02 14:21:11.000000000 +0200 @@ -0,0 +1,9 @@ +/* PR driver/81650 */ +/* { dg-do compile } */ +/* { dg-options "-Walloc-size-larger-than=9223372036854775807" } */ + +void * +foo (void) +{ + return __builtin_malloc (5); +} Jakub